Improve device list for flashing via WiFi

Related to #749

Please improve the device listing to show the real devices discovered with MDNS.
Having a `Default (10.0.0.1)` entry there is really misleading, as it suggests that no device has been found.
It's a surprise for the user that flashing actually works even with this default entry.

The list should show the real IP of the found device that's going to be flashed.

Thanks.
